It is disclosed in Japanese Patent Laid Open Sho 53-24400, U.S. Pat. No. 4,400,340 and U.S. Pat. No. 4,426,502 that ring-opening polymerization of a cycloolefin containing norbornene moiety, e.g. dicyclopentadiene (called "DCP" hereinafter), in the presence of a metathesis polymerization catalyst system produces a cross-linked polymer containing olefinic groups in the main chain.
Said Japanese Patent Laid Open Sho 53-24400 discloses polymerization of DCP with or without other cycloolefin or norbornene type monomer in the presence of a metathesis polymerization catalyst system, and there is disclosed therein the use of a variety of norbornene type monomers including the monomer ##STR1## wherein R is a substituent such as alkyl and aryl groups. However, this Japanese Patent Laid Open Sho 53-24400 is characterized by per se a new metathesis catalyst system, and polymerization of DCP, etc. is accomplished with a hydrocarbon solvent. DCP polymer prepared therein is recovered from the solvent and then is used to produce a molded article. This means that DCP polymer prepared by using the catalyst is substantially no-crosslinked thermoplastics.
Said U.S. Pat. No. 4,400,340 and U.S. Pat. No. 4,426,502 disclose the production of a molded article by injecting a reactive liquid mixture comprising norbornene-type monomer such as DCP and a metathesis polymerization catalyst system into a mold in which said liquid mixture is metathesis polymerized in bulk (called "RIM process" hereinafter). RIM process is a low pressure one-step or one-shot injection of a liquid mixture into a closed mold where rapid polymerization occurs resulting in a molded article. Thus, there are easily produced large-sized molded articles by RIM process from DCP and the like. The molded articles have been taken notice from the industrial point of view since they have attractive physical properties as balanced in stiffness and impact resistance.
The metathesis polymerization catalyst system used in RIM process comprises a catalyst component comprising a compound of a transition metal such as tungsten, molybdenum, rhenium or tantalium and an activator component comprising an organic metal compound of aluminum, tin or the like. The metathesis polymerization catalyst system initiates the polymerization reaction upon mixing of the catalyst component and the activator component. RIM process utilizes advantageously characteristics of the metathesis polymerization catalyst system, and therein there is produced a molded article by mixing the first reactive solution containing the catalyst component and a monomer such as DCP and the second reactive solution containing the activator component and the monomer and then immediately injecting the mixture into a mold.
However, both of the catalyst component and the activator component of said catalyst system are too active for polymerizing a cycloolefin such as DCP in bulk even at room temperature, and thus the polymerization of DCP and the like often occurs before poured into a mold and it makes the pouring of the mixture into the mold difficult.
Therefore, it is desirable to moderate the metathesis polymerization reaction as to provide an adequate induction period.
Said U.S. Pat. No. 4,400,340 discloses using Lewis-bases to moderate the polymerization reaction of RIM process. However, Lewis-bases remaining in the polymer injure molded polymer articles and often produce undesired volatile compounds.
Said U.S. Pat. No. 4,426,502 is characterized by the use of a particular metathesis polymerization catalyst system to moderate the polymerization reaction of RIM process. However, this requires the inconvenient limited selection of the metathesis polymerization catalyst system.
Recently, there has been produced a molded article by so-called "pre-mix process" which comprises mixing a metathesis polymerization catalyst system and a monomer such as DCP to prepare a pre-mixture and then introducing the pre-mixture into a mold.
A molded article can be produced more easily by pre-mix process than by RIM process, since pre-mix process requires simpler molding devices than in RIM process. However, pre-mix process also often necessitates the more effective moderation of the metathesis polymerization reaction than RIM process.
Now, we have found that norbornene-type monomers containing at least one Lewis-base group in the structure can moderate the metathesis polymerization reaction in bulk of DCP and at the same time can act as a metathesis polymerizable comonomer resulting in a copolymer in which a low molecular weight Lewis base does not substantially remain. Thus, it is very advantageous to use in RIM process and pre-mix process such monomers containing Lewis-base group.
Further, we have found that a norbornene-type monomer containing at least one N-substituted 5-membered cyclic imide group (called "ICN" hereinafter) is more useful among said norbornene-type monomers containing Lewis-base group, since such imide group can effectively moderate the metathesis polymerization reaction and the introduction of the imide group provides the polymer with improved mechanical and chemical properties.
Therefore, it is an object of the present invention to provide a process for producing a molded article by the metathesis polymerization of DCP with ICN to moderate the metathesis polymerization reaction. A further object is to provide a multi-part polymerizable composition used for producing the molded article. Another object is to provide a molded article and a crosslinked polymer produced by the process.